In an unusual turn of events, Jimmy Fallon had a lot of thoughts about President Trump during “The Tonight Show” on Monday.

Fallon normally tries to stay out of politics, but he had no choice: On Sunday night, Trump fired off a critical tweet at the late-night host, mocking Fallon for saying he regretted an infamous interview between the two in 2016. Fallon received enormous backlash for the lighthearted conversation and playfully mussing Trump’s hair, and recently said on a Hollywood Reporter podcast that it was “a mistake” and he wished he would have handled the situation differently.

“Before we begin,” Fallon said at the top of his monologue, “I just want to give a shout out to our show’s No. 1 fan: the president of the United States!”

The audience laughed appreciatively. “As you may have heard, last night, the president of the United States went after me on Twitter,” Fallon said. “So Melania, if you’re watching, I don’t think your anti-bullying campaign is working.”

Fallon continued: “When I saw that Trump insulted me on Twitter, I was gonna tweet back immediately, but I thought, ‘I have more important things to do.’ Then I thought, ‘Wait, shouldn’t he have more important things to do? He’s the president! What are you doing? You’re the president! Why are you tweeting at me?!'”

Fallon showed the tweet to the audience:

“That’s real. It’s crazy. The president went after me on Twitter. It’s pretty much the only thing I have in common with NFL players,” Fallon said. He then echoed what he tweeted in response on Sunday: He made a donation in Trump’s name to the Refugee and Immigrant Center for Education and Legal Services, which helps immigrant families.

When Fallon sat down at his desk after the monologue, he continued the story, filling in some of the context. He said most of the Hollywood Reporter podcast was about the past year on “The Tonight Show,” and then in the last five minutes, he talked about the 2016 Trump interview. At the time, Fallon didn’t think tousling Trump’s hair was a big deal. But the intense backlash left him depressed.

“Now, I’m not depressed. That was two years ago. I have a show to do. I’m paid to make people laugh. I have to get over it and move on, and that’s my job,” Fallon told the audience. “It’s to make you have a good time and forget about this stuff. I’m a total goofball. There’s nothing else I want to do. That’s all I’m here to do, is make you happy.”

Fallon also addressed the last part of Trump’s tweet, which seemed to imply that Fallon called him after the episode and said “monster ratings.” Fallon looked flummoxed.

“First of all, I’ve never called this human in my life. I don’t have his number. I don’t want his number,” Fallon said. “And ‘monster ratings’? . . . I’ve never said ‘monster ratings.’ I don’t know what he’s talking about.”

“By the way, Donald. I don’t know if you’ve seen my ratings the past two years — you didn’t help my ratings,” he added dryly. “But really, thanks a lot. Thanks for nothing.”

Indeed, if anything, Fallon has fallen behind his more politically inclined competition — CBS’s “Late Show With Stephen Colbert” is now No. 1 in total viewers.

Meanwhile, at a rally in South Carolina on Monday night, Trump was still talking about Fallon and ratings.

“He looks like a lost soul. But you know what, he’s a nice guy. I agreed to do his show, and because I guess I was running at the time, he got tremendous ratings on that show,” Trump said, according to Variety. “He should be thankful. He shouldn’t be upset and angry.”

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